44 research outputs found
Filtration performance of ultrathin electrospun cellulose acetate filters doped with TiO<sub>2</sub> and activated charcoal
Air filters are crucial components of a building ventilation system that contribute to improving indoor air quality, but they are typically associated with relatively high pressure drops. The purpose of the study is to evaluate the effect of additives on ultrathin electrospun filters, the pressure drop, and the particle removal efficiency of uniformly charged particles. The fibres were electrospun under optimised conditions that resulted in a fast-fabricating process due to the properties of the cellulose acetate solution. Different ultrathin electrospun fibre filters based on cellulose acetate (CA) were fabricated: a pure CA electrospun fibre filter, two filters based on CA fibres separately doped with activated charcoal (AC) and titanium dioxide (TiO2), respectively, and a composite filter where the two additives, AC and TiO2, were embedded between two CA fibres layers. The ultrathin filters exhibited a low pressure drop of between 63.0 and 63.8 Pa at a face velocity of 0.8 m sâ1. The filtration performance of uniformly charged particles showed a removal efficiency above 70% for particle sizes between 0.3 and 0.5 ÎŒm for all filters, rising above 90% for larger particles between 1 and 10 ÎŒm, which translates to the average sizes of pollens and other allergenic contaminant particles. Due to the positive impact on the fibre morphology caused by the additives, the composite filter showed the highest filtration performance among the produced filters, reaching 82.3% removal efficiency towards smaller particles and a removal of up to 100% for particle sizes between 5 and 10 ÎŒm. Furthermore, cellulose acetate itself is not a source of microparticles and is fully biodegradable compared to other polymers commonly used for filters. These ultrathin electrospun filters are expected to be practical in applications for better building environments
Sedimentary Evolution and Provenance of the late Permian-middle Triassic Raggyorcaka Deposits in North Qiangtang (Tibet, Western China): Evidence for a Forearc Basin of the Longmu Co-Shuanghu Tethys Ocean
The tectonic origin of the >500âkmâlong EâW trending Central Qiangtang metamorphic
belt (CQMB), which separates the North Qiangtang block (NQB) and South Qiangtang block (SQB),
remains controversial. Moreover, the coeval geological evolution of the southern NQB has been poorly
investigated, particularly its tectonic relationship with the CQMB. Here we present stratigraphic,
sedimentary, and provenance analyses of the late Permianâmiddle Triassic depositional succession at
Raggyorcaka in the southern NQB and test two radically different hypotheses for origin of the CQMB.
A complete marine transgressionâregression sequence with twoâsided provenance characterizes the late
PermianâTriassic sedimentary rocks in the southern NQB. Sandstone petrological analyses reveal a
prominent provenance transition to an active volcanic source beginning in the late Changhsingian.
Detrital zircon UâPb geochronological results of the transgression subsequence show a concentrated
youngest zircon group of 236â288 Ma (peak at ~248.1 Ma), with negative ΔHf(t) values (â25.3 to â0.2)
and large Hf crustal model ages (TC
DM; 1,311â2,887 Ma). These new findings show that the
Raggyorcaka sequence was most likely deposited in an active continental margin. Combined with
other evidence, we further infer that the CarboniferousâTriassic successions of the southern NQB were
most likely deposited in a forearc basin under the in situ suture model, that is, the northward
subduction of the Longmu CoâShuanghu Tethys Ocean beneath the NQB. Moreover, the detrital zircon
age distribution of the southern NQB suggests that the NQB probably drifted from the Gondwana
supercontinent in the early Paleozoic and became adjacent to periâCathaysian blocks no later than the
CarboniferousOur field work was supported by the
Young Scientist Fund of the National
Natural Science Foundation of China
(Grant 41402177). The experimental
items were financially supported by the
China Geological Survey (CGS):
â1:50,000 regional geological surveys in
the Gangmari area of Tibetâ (Grant
1212011086062) and the Ministry of
Education of the People's Republic of
China (Grant 649199111027)
Understanding the Lateral Drifting of an Erupting Filament with a Data-constrained Magnetohydrodynamic Simulation
Solar filaments often exhibit rotation and deflection during eruptions, which
would significantly affect the geoeffectiveness of the corresponding coronal
mass ejections (CMEs). Therefore, understanding the mechanisms that lead to
such rotation and lateral displacement of filaments is a great concern to space
weather forecasting. In this paper, we examine an intriguing filament eruption
event observed by the Chinese H{\alpha} Solar Explorer (CHASE) and the Solar
Dynamics Observatory (SDO). The filament, which eventually evolves into a CME,
exhibits significant lateral drifting during its rising. Moreover, the
orientation of the CME flux rope axis deviates from that of the pre-eruptive
filament observed in the source region. To investigate the physical processes
behind these observations, we perform a data-constrained magnetohydrodynamic
(MHD) simulation. Many prominent observational features in the eruption are
reproduced by our numerical model, including the morphology of the eruptive
filament, eruption path, and flare ribbons. The simulation results reveal that
the magnetic reconnection between the flux-rope leg and neighboring low-lying
sheared arcades may be the primary mechanism responsible for the lateral
drifting of the filament material. Such a reconnection geometry leads to
flux-rope footpoint migration and a reconfiguration of its morphology. As a
consequence, the filament material hosted in the flux rope drifts laterally,
and the CME flux rope deviates from the pre-eruptive filament. This finding
underscores the importance of external magnetic reconnection in influencing the
orientation of a flux rope axis during eruption.Comment: 25 pages, 14 figures, Accepted for publication in Ap
Maintenance of estuarine water quality by mangroves occurs during flood periods: A case study of a subtropical mangrove wetland
Seasonal changes in water quality were measured in samples taken at various distances from shallow water across mudflat to mangroves during flood period and from mangroves across mudflat to shallow water during ebb period in a subtropical mangrove estuary (Zhangjiang Estuary, Fujian, China). The TN (total dissolved nitrogen), TP (total dissolved phosphorus), COD (chemical oxygen demand), and DOC (dissolved organic carbon) contents during the flood period were significantly higher than those during the ebb period. In contrast, the opposite was true for the POC (particulate organic carbon) content and transparency. The mangroves at Zhangjiang Estuary may trap nutrients at rates of 90.5 g N/m(2)/yr, 2.2 g TP/m(2)/yr, and 13.7 g C/m(2)/yr in the form of DOC, and export POC at a rate of 81.8 g/m(2)/yr. Our results support the hypothesis that the maintenance of estuarine water quality by mangroves occurs during flood periods. (C) 2010 Elsevier Ltd. All rights reserved.Natural Science Fund of China [40876046, 40376025]; Fujian Province Universit
Robust estimation of bacterial cell count from optical density
Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data
Giant Induan oolite: A case study from the Lower Triassic Daye Formation in the western Hubei Province, South China
AbstractMost Phanerozoic oolites are marked by ooids with a diameter less than 2Â mm. Observations on a Neoproterozoic oolite have resulted in a change of concept. The term âpisoliteâ that traditionally referred to oolites with a grain size of more than 2Â mm, is now restricted to those coated carbonate grains formed by meteoritic freshwater diagenesis; oolites with a grain size of more than 2Â mm are now defined as âgiantâ. Particular unusual giant oolites within a set of oolitic-bank limestones with thicknesses of more than 40Â m in the top part of the Lower Triassic (Induan) Daye (Ruiping) Formation at the Lichuan section in the western part of Hubei Province in South China, represent an important sedimentological phenomenon in both the specific geological period and the geological setting that is related to the end-Permian biological mass extinction. Like the giant oolites of the Neoproterozoic that represent deposits where oolites formed in a vast low-angle carbonate ramp at that special geological period, the Triassic Daye Formation at the study section are significant because they provide a comparative example to help understand the evolving carbonate world reflected by oolites, the origin of which is still uncertain, and they give insight into the sedimentation pattern of the desolate sea floor, which resulted from the mass extinction at the turn of the Permian into the Triassic
Fabrication of PANI/C-TiO2 Composite Nanotube Arrays Electrode for Supercapacitor
Polyaniline/carbon doped TiO2 composite nanotube arrays (PANI/C-TiO2 NTAs) have been prepared successfully by electrodepositing PANI in C-TiO2 NTAs which were prepared by directly annealing the as-anodized TiO2 NTAs under Ar atmosphere. The organic residual in the TiO2 NTAs during the process of anodization acts as carbon source and is carbonized in Ar atmosphere to manufacture the C-TiO2 NTAs. The specific capacitance of the PANI/C-TiO2 electrode is 120.8âmFâcmâ2 at a current density of 0.1âmAâcmâ2 and remains 104.3âmFâcmâ2 at a current density of 2âmAâcmâ2 with the calculated rate performance of 86.3%. After 5000 times of charge-discharge cycling at a current density of 0.2âmAâcmâ2, the specific capacitance retains 88.7% compared to the first cycle. All these outstanding performances of the as-prepared PANI/C-TiO2 NTAs indicate it will be a promising electrode for supercapacitor